Graduate Thesis Or Dissertation

 

Host and Pathogen Contributions to the Populus–Sphaerulina Pathosystem Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/vd66w6367

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  • Sphaerulina musiva is a fungal pathogen that causes Septoria leaf spot and stem canker on susceptible Populus species and hybrids. In this thesis, host and pathogen contributions to Septoria stem canker disease were explored through: 1) a greenhouse study associating Septoria stem canker phenotypes with molecular markers from a genetic linkage map of a Populus trichocarpa × Populus deltoides F2 pseudo-backcross population; and 2) the development of a protocol facilitating the genetic transformation of S. musiva by Agrobacterium tumefaciens¬. The QTL study localized a single, significant QTL to Linkage Group 16, consistent with currently unpublished reports (Simon et al., unpublished). Additionally, evidence (p = 0.417; p = 0.952) was obtained that the segregation of resistant-to-susceptible stem canker disease severity was not significantly different from the expected 1:1 ratio, supporting the hypothesis that Septoria stem canker resistance is recessive. Genes within a 1000-Kb window centered on the significant marker on Linkage Group 16 were analyzed for indications of positive selection (Ka/Ks > 1) and immune-related gene annotations; several candidate genes are discussed. The second chapter describes the development of a protocol for the genetic transformation of S. musiva through co-cultivation of S. musiva conidia with A. tumefaciens cells carrying a binary vector. Using the methods described, transformants were generated. Evidence supports the conclusion that random insertion of a hygromycin resistance cassette into the genome of S. musiva isolate MN-14 was successful. However, our attempts at gene-disruption transformation (by homologous recombination into a nrps1 gene) appear to have failed, though integration of the hygromycin resistance cassette was detected elsewhere in the genome by PCR. Recommendations for further protocol development are discussed. Finally, the implications of the greenhouse QTL study and S. musiva transformation are explored in consideration of management implications and future research.
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  • FERM Fellowship
  • College of Forestry Fellowship
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  • Pending Publication
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  • 2020-01-02 to 2022-03-09

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